In a conventional wireless headphone or cable earphone having a microphone, a volume control knob is generally coupled to an ear muff on a side of the headphone or earphone, and the microphone is installed at a predetermined position, such that the microphone can be adjusted to an appropriate position according to a user's using habit. In general, a link rod is used for connecting the ear muff and the microphone, such that when an end of the link rod is coupled to a connecting portion of the link rod of the ear muff, it is necessary to use another fixing element such as a screw, a nut, and the like to make the connecting portion of the link rod as a rotatable and contractible structure. In the foregoing conventional design of installing the volume control knob on the ear muff and the connecting portion of the link rod separately, the number of components is increased significantly, the assembled structure is complicated, the cost is high, and the aesthetic appearance of the headphone is affected adversely.